Naturally I'd say: NO! Janeway doesn't need scars to be sexy! But I do agree. It suits her. Lots of fanfic is usually about having her injured in one way or the other - to make her vulnerable and set an inviting frame for certain interactions with certain crew members. An attempt to peel the captain off the woman.

To cite teacake here: "She can be tightly wound. Control, she's her hardest taskmaster. I suppose that's part of the appeal, unwinding her.."

Speaking of appeal:
I always found the idea of two Janeways highly interesting. There is even fanfic about it. (Although I was a bit disappointed, when I read that story.)